100% financing is tough...even for private lenders, unless there are compensating factors (great track record, proven successes, strong reserves, great credit score...maybe even good job/w2 income (usually not a factor for non-bank investment property lenders, but may be for a private individual)). 

Is there certain criteria for portfolio loans and are they mostly acquired through local banks?

etc..You can try to go conventional, to a community bank/portfolio lender, or to a non-bank lender for the above. 

We ending up putting 25% down on a commercial loan with a local bank.

Is there any typical reasons why the bank as not listed them for sale?

I'm looking to borrow $50k for the down payment and plan on financing the rest with my local bank.

You can also go the community bank route a look for a portfolio loan, which will give you flexibility to expand/borrow on more properties.

Your family member could also provide the financing on it and make money every month with a positive cash flow spread between the debt and the rent collected or be like a guarantee person that is the main backer for the long term loan your Bank or other lender that  owns that property with a long term loan with that property  on a security  loan until that loan is paid off.Not saying the fix up budget makes this decision fairly difficult but i would say to not have a house that needs over $5,000 on the "make ready" expense to make a 20% gross return giving a cost price and sales price you gave on your example.What you could do to find a deal is pretty limitless. 

With all the great commercial loan programs out there, if it were me, I'd search different banks for a Stated Income ALT program up to 90% cLTV with rates in the 4 to 5 range Questions:Are you paying cash?

ask for last 3 years bank statements, signed estoppel statements, and/or a signed purchase agreement that explicitly indicates the gross and/or net income of the park is true and accurate.